Mój brat podnosi ciężką torbę.

Because brat is a masculine singular noun, and the possessive word mój has to agree with the noun it describes.

A useful point for English speakers: Polish possessives agree with the thing possessed, not with the owner.

• mój brat = my brother
• moja siostra = my sister
• moje dziecko = my child

So here, brat is masculine, so mój is the correct form.

Brat is in the nominative singular.

That is the basic form of the noun, and it is used here because brat is the subject of the sentence — the person doing the action.

So:

• brat = nominative singular
• it answers the question who is lifting?
• answer: mój brat

Because torba is the direct object of the verb, so it goes into the accusative case.

The dictionary form is:

• torba = bag

But in this sentence:

• podnosi torbę = is lifting a bag / the bag

For many feminine nouns ending in -a, the accusative singular changes to -ę:

• torba → torbę
• książka → książkę
• kobieta → kobietę

So torbę is simply the accusative form of torba.

Because adjectives in Polish must agree with the noun they describe in:

• gender
• number
• case

The noun torbę is:

• feminine
• singular
• accusative

So the adjective must match it:

• dictionary form: ciężki = heavy
• feminine nominative: ciężka
• feminine accusative: ciężką

That is why you get:

• ciężka torba = a heavy bag
• podnosi ciężką torbę = is lifting a heavy bag

Podnosi is the 3rd person singular present form of the verb podnosić.

So it means:

• he lifts
• he is lifting
• she lifts / is lifting
• it lifts / is lifting

Here, because the subject is mój brat, it means he lifts / he is lifting.

The breakdown is:

• podnosić = to lift, to raise
• podnosi = he/she/it lifts, is lifting

It can mean either, depending on context.

The Polish present tense often covers both:

• right now: My brother is lifting a heavy bag
• habitually / generally: My brother lifts a heavy bag

Without extra context, Polish does not force a distinction here.

If you want to make it clearer, you can add words like:

• teraz = now
• często = often
• codziennie = every day

For example:

• Mój brat teraz podnosi ciężką torbę = My brother is lifting a heavy bag now.
• Mój brat często podnosi ciężką torbę = My brother often lifts a heavy bag.

It is imperfective.

That matters because in Polish, aspect is very important.

• podnosić = imperfective, focuses on the action as ongoing, repeated, or general
• the perfective partner is usually podnieść

So:

• podnosi = is lifting / lifts
• podniesie = will lift

A learner does not need to master all aspect rules at once, but it is good to notice that podnosi comes from the imperfective verb.

Because Polish has no articles.

English uses:

• a bag
• the bag

Polish just says:

• torba
• torbę

Context tells you whether the meaning is more like a or the.

So ciężką torbę could mean:

• a heavy bag
• the heavy bag

Both are possible, depending on the situation.

Yes. Polish word order is more flexible than English because case endings show what each word is doing.

The sentence Mój brat podnosi ciężką torbę is a very natural, neutral order:

• subject + verb + object

But you could also say things like:

• Ciężką torbę podnosi mój brat
• Podnosi mój brat ciężką torbę

These are grammatically possible, but they change the focus or emphasis.

For a learner, the safest default is:

• subject + verb + object

So the original sentence is a good standard pattern to copy.

You can say Brat podnosi ciężką torbę, but it usually sounds less natural unless the context already makes it clear whose brother you mean.

In many situations, Polish drops words that are understood from context, but mój is often kept when introducing or identifying someone clearly.

So:

• Mój brat podnosi ciężką torbę = clear and natural
• Brat podnosi ciężką torbę = possible, but more context-dependent

You would usually look up their base forms:

• torbę → torba
• ciężką → ciężki

That second one can be tricky for English speakers. Adjectives are usually listed in dictionaries in the masculine nominative singular form, so even though the sentence has ciężką, the headword is normally ciężki.

So the dictionary forms are:

• torba = bag
• ciężki = heavy

These letters often catch English speakers’ attention.

• ó in mój is pronounced like Polish u
• ę in torbę is a nasal vowel, but in normal speech its pronunciation can weaken depending on the following sound
• ą in ciężką is also a nasal vowel, and before certain consonants it may sound more like a vowel plus a nasal consonant

A simple learner-friendly approximation is:

• mój sounds roughly like moo-y with a short glide
• torbę sounds roughly like TOR-beh with a nasal quality at the end
• ciężką is harder, roughly CHENZH-kohm or CHYENSH-kohm, depending on how carefully it is pronounced

The most important thing at an early stage is to:

• recognize ó as sounding like u
• notice that ę and ą are nasal vowels
• not worry if your pronunciation is not perfect yet

Because ciężką torbę is the object phrase, while mój brat is the subject phrase.

In this sentence:

• mój brat stays in the nominative because it is the subject
• ciężką torbę goes into the accusative because it is the direct object

Polish marks these roles with endings. That is why:

• mój brat stays in its basic subject form
• ciężka torba changes to ciężką torbę

This is one of the biggest differences from English: the function of a word in the sentence often changes its ending.